H2s reducing process for polycyclic endoquinones and partial reduction products thereof



United States Patent N 0 Drawing. Filed Dec. 7, 1959, Ser. No. 857,494 13 Claims. (Cl. 260-580) This invention relates to a process for the preparation of polycyclic aromatic hydrocarbons and their derivatives from polycyclic quinones. More specificall it relates to a process of reducing the quinoid carbonyls of polycyclic quinones, other than ortho quinones and quinones in which the quinoid carbonyls are both in the same ortho benzo ring, or alternatively oxygenous reduced forms of the quinoid carbonyl system of such quinones to the corresponding hydrocarbons by heating the said compounds to from 75 to 250 C. with hydrogen sulfide in the presence of an acid catalyst under substantially anhydrous reaction conditions.

Polycyclic aromatic hydrocarbons occur naturally in coal tar, but the isolation of these in a pure form is often difiicult and derivatives are sometimes not easy to obtain. Polycyclic aromatic hydrocarbons are also found in the product from the catalytic cracking of petroleum distillates and in the hydrogenation of coal. From all these sources their commercial recovery is frequently not practical and it is diificult to obtain them in a pure state. In the past, the most important method for the preparation of momatic fused ring hydrocarbons has been the reduction of the corresponding quinones with zinc dust. This reduction has been carried out in a number of ways. In one procedure the quinone is distilled with zinc dust, the hydrocarbon distilling over. This process works well with the smaller ring systems but where the hydrocarbon boils at a high temperature the yield is very small. In another procedure the quinone is heated at ZOO-300 C. with zinc dust in a melt of zinc chloride and sodium chloride, but this procedure tends to form bi-molecular by-products from which the separation of the desired product is troublesome. In another method the quinone is heated in boil-ing pyridine with zinc dust followed by the slow addition of acetic acid. This requires purification of the product from high boiling solvents or by vacuum sublimation.

We have found a procedure of converting polycyclic quinones or oxygenous reduction products thereof to the corresponding hydrocarbon which is highly practical and allows the isolation of the products in good yields and purity. In the process of our invention polycyclic quinones, other than ortho quinones and quinones in which the quinoid carbonyls are both in the same ortho benzo ring, or the oxygenous reduction products of such quinones are heated with hydrogen sulfide under anhydrous conditions in the presence of an acid catalyst.

There are certain limitations on the starting materials of our invention. First of all, the reaction does not go with ortho quinones such as, for example, phenanthraquinone. Consequently it is specified in the claims of this application that the quinone be an endo-quinone. 'I he prefix endois used in chemistry to indicate the bridging of a ring by a group attached to two places on the ring other than the two vicinal carbons. It is used in a similar sense, in this application, with respect to the quinones to indicate a quinoid structure in which the quinoid carbonyls are not vicinal to one another. Another limitation is that the quinoid carbonyls may not be both on the same ortho benzo ring. An example of what is meant by this is naphthoquinone. Other such com- 3,109fi27 Patented Oct. 29, 1963 pounds would be formed by fusing rings to the 6,5, 6,7 and/or 7,8 positions of a naphthoquinone. The quinoid carbonyls in naphthoquinone or in such fused derivatives of naphthoquinone are in an ortho benzo ring and it has been found that such quinoid structures do not reduce in the process of our invention but instead give sulfur containing reaction products. Similarly benzoquinone itself is not operative. Another way of defining the endoquinones which are operable is to state that any atomic configuration which occurs in the endo-quinone is in a ring in which X and Y are part of a further fused aromatic ring system.

It is most surprising that the polycyclic quinone will react with hydrogen sulfide under the conditions of our invention to give hydrocarbons instead of reacting to introduce sulfur into the ring. Since it is well known that carbonyl compounds such as ketones, including aryl ketones, normally react with hydrogen sulfide in the presence of acid catalysts to give the corresponding thio compounds, usually in a polymerized state. Such reactions are reported, for example, in Kirk-Othmer Encyclopedia of Chemical Technology, volume 13, page 390 and in M-igrdichian Organic Synthesis, page 130 and is apparently the sort of reaction which is observed with benzoquinone, and naphthoquinone.

In the-process of our invention a polycyclic quinone or substituted quinone or partially reduced quinone is reacted with hydrogen sulfide in the presence of the acid catalyst at a temperature from 75250 C. When the reaction is finished, the resulting hydrocarbon or sub stituted hydrocarbon is separated from the catalyst, excess hydrogen sulfide, and the by-product sulfur by various means. Normally the reaction mixture is washed or extracted with water to remove the acid catalyst and other water soluble material. The residue may then be extracted with an aqueous solution of sodium sulfide and caustic soda to remove the by-product sulfur. The hydroca-rbon may be purified to any degree desired by the standard methods such as sublimation or recrystallization. The fundamental reaction occurring in our process can be illustrated by the following equation describing the production of anthracene from anthraquinone.

The process of our invention can be used to prepare a wide variety of aromatic hydrocarbons and their derivatives having more than two rings. The polycyclic qui nones which are used as a starting material may have substituen-ts in other parts of the molecule. Many such substituents do not react with hydrogen sulfide under the reaction conditions. Others react in their own way, independently of the reduction process and do not interfere at all with the reduction of-the quinone to the hydrocarbon. Aryl, alkyl, amino and halogen groups thus pass through the reduction process unaifected. Such substituents as nitro, carbonyl, and hydroxy groups react independently with some of the hydrogen sulfide. Thus a nitro anthraquinone reduces to an amino anthracene, the nitro also being reduced. A hydroxyanthraquinone will produce a mercapto hydrocarbon, the hydroxyl group Acid Catalyst being replaced by the mercapto group, which of course can react further with itself or with other groups to form sulfides and the like. Carboxyl groups are converted into thiocarboxyl groups and carbonyl groups are converted into thiocarbonyls or gem-dithi-ols. These reaction products can also react further to the extent that such further reaction will complicate the reduction process, their presence is preferably avoided. They do not, however, interfere with the main process of our inventon, the reduction of the quinone to the hydrocarbon.

The quinone must be, as previously stated, an endoquinone in which the quinoid carbonyls are not in the same 'ortho benzo ring. The quinone may be in fully oxidized quinoid state or in the partially reduced state such as the anthrones, hydroquinones and the quinhydrones. We refer to all of these partially reduced quinones collectively as oxygenous reduction products of the quinoid system. Examples of such oxygenous reduction products of anthraquinone, for example, are anthrone I, anthrahydroquinone II, and anthraquinhydrone III.

i H: OH

I II

and

Quinones which can be used as starting materials include the following: Anthraquin-one, 6,12-chrysenedione, dibenz[a,h]anthracene-7,14-dione, naphthacenequinone, 5,11-naphthacenedione, 6,13 -pentacenedione, 5,6,12,14- pentacenetetrone, 7,16 heptacenedione, 5,7,9,14,16,l8- heptacenehex-one, dibenzo[a,j]perylene 8,16 dione, dibenzo[a,h]pyrene 7,14 dione, dinapthth[2,3-a,2,3-h]- anthracene 5,9,14,18 tetrone, dibenzo[b,k]chrysene- 5,8,13,16-tetrone, anthranthro-ne, violanthrone, pyranthrone, dinaphtho [l,2,3-cd,l',2',3,-jk] pyrene 8,16- dione, and dinaphtho[2,3-b,2',3-j] pyrene 5,9,14,18- tetrone.

We may also use substituted quinones such as 2-chloroanthraquinone, 1-chloro-2-methylanthraquinone, l-nitroanthraquinone, l-amino-anthraquinone, 6-phenylnaphtha cenequinone, 5,14-dirnethyl-6,l3-pentacenedione, 16,17- dimethylviolanthrone, 3-methyl 8,16 pyranthrenedione and 11 methylanthra[1,2-b]phenanthrene 5,8,13,14- tetrone. The quinone may also contain heterocyclic systems in a non-quinoid part of the molecule, such as a naphtho [2,3-g]quinoline 6,7 dione and 3-arninoanthra- [2,3-b]-benzo[d]furan-7,l2-dione. Other examples of the reduced forms of quinones are Z-methylanthrone, dibenz[a,j]anthracene- 7 (14) one, 5(12) -naphthacenone, 6(13)-pentacenone and anthrahydroquinone.

The acid catalysts used in the process of our invention are easily available organic sulfonic acids or certain of the common mineral acids. Most conveniently, one uses the aliphatic sulfonic acids such as ethane sulfonic acid, propane sultonic acids, butane sulfonic acid, hexanesuh fonic acid, octane sulfonic acid, dodecane sulfonic acid, octadecane sulfonic acid, or mixtures thereof usually ob-' tained by the reaction of sulfuric acid with unsaturated hydrocarbons such as is obtained from petroleum cracking and Whichare usually sold under the name of mixed alkane sul fonic acids, or aromatic sulfonic acids of less than three carbocyclic six membered rings, such as benzenesu-lfonic acid, ortho-, meta, or para-toluenesulfonic acids and mixtures thereof, or naphthalene mono, di, and

( III trisulfonic acids or biphenyl sulfonic acid, and the like. Non-oxidizing inorganic acids such as sulfuric acid, phosphoric acid, poly phosphoric acid, and the like may also be used. It must, of course, be a non-oxidizing acid under the reaction conditions since this reaction of our invention is a reduction. The minimum usage of catalyst in the reaction of our invention is 0.1 part by weight of catalyst per part by weight of quinone. In practice we use from 2.5-5 parts of catalyst per part of quinone. Langer amounts can be used but are not necessary and increase the cost of the process.

The theoretical minimum usage of hydrogen sulfide is 3 moles of hydrogen sulfide per mole of quinone (that is, per pair of carbonyls). Normal-1y it is considered advantageous to use an excess of the hydrogen sulfide. In practice We have [found it convenient to use from 125 moles to as much as 4,000 moles of hydrogen sulfide per mole of quinone, and as much as 88 moles of hydrogen sulfide per mole of an anthrone. The function of such large excesses is, of course, to increase the speed of the reaction, since with a theoretical quantity the necessary contact between the hydrogen sulfide and the quinone is necessarily small and therefore the rate of reaction is slow. Another function of such excesses is to make certain that enough hydrogen sulfide is present for the reduction of the quinoid carbonyls even though other groups reactive with hydrogen sulfide are present and therefore compete with the quinoid carbonyls in the reaction.

This application is a continuation-in-part of Serial No. 768,842, filed October 22, 1958 and now abandoned.

Temperatures ranging from -250" C. may be used in the process of our invention. We however prefer to use the temperatures in the range of -125 C. It is obviously advantageous to carry out this reaction in a closed system at a superatmospheric pressure, although the reaction may be carried out at atmospheric pressure. In the latter case the hydrogen sulfide usage is greater since it must be passed through constantly and only a very small proportion of the hydrogen sulfide comes into reactive contact with the other reactants.

The process of our invention is carried out under substantially anhydrous conditions. Normally a solvent is not used and the catalyst and the excess hydrogen sulfide serve as the only solvents available. However, the reaction can be carried out in the presence of an inert organic solvent provided it has sufficiently high a boiling point to remain liquid at the reaction temperature. Reaction conditions are stated to be substantially anhydrous because the alkyl and aryl su lfonic acids which are normally used as the preferred acid catalyst are seldom obtained in a pure anhydrous form. However, as long as there is no more water present in the sulfonic acids or in sulfuric acids or phosphoric acids or catalyzed reaction mixtures than would form a mono-hydrate of the said acid catalyst, the catalyst is efiective. Greater amounts of water than this inhibit the reactions.

Our invention can be further illustrated by the following examples in which parts are by weight unless otherwise specified. Parts by volume are to parts by weight as one cubic centimeter is to one gram.

Example 1 autoclave at -95 C. until the reduction is substantiallycomplete. The reaction product is washed with O 400 parts of water. The filter cake is slurried in a hot solution of 30 parts of sodium sulfide nonahydrate in 120 parts by volume of 20% caustic soda solution. The product is isolated by a 'hot filtration, followed by a water wash and drying. The product after recrystallization, is found by mixing melting point, infrared spectra and inertness to hydrosulfite reduction to be anthra cene free of anthraquinone.

When mixed alkane sulfonic acids, xylenesulfonic acid, naphthalene-2,6-disulfonic acid, sulfuric acid, phosphoric acid, or polyphosphoric acid is substituted for the toluenesulfonic acid in the same quantity, a similar result is obtained.

Example 2 A reaction mixture containing 19.4 parts of anthrone, 50 parts of toluenesulfonic acid mixed isomers, and 300 parts of hydrogen sulfide is heated in an autoclave at 85 C. unt l reduction is substantially complete. The product is washed with water and dried in air. This material is twice crystallized from benezene to give anthracene melting at 208-209 C.

Example 3 (I) $02 NH2 A reaction mixture containing 18.7 parts of 1-nitroanthraquinone, 50 parts of toluenesulfonic acid mixed isomers, and 310 parts of hydrogen sulfide is heated in an autoclave at 90 C. until reduction is substantially complete. After washing with 2000 parts of Water made alkaline with caustic soda and drying, l-aminoanthracene is obtained.

Example 4 sodium sulfide and sodium hydroxide and then isolated by filtration to give l-aminoanthracene.

Example 5 CHa A reaction mixturecontaining parts of l-chloro- 2-methylanthraquinone, 50 parts of toluenesulfonic acid mixed isomers and 340 parts of hydrogen sulfide is heated in an autoclave at 100 C. until reduction is substantially complete. The reaction product is washed with 300 parts of water, and the water-insoluble material is extracted with 100 parts by volume of a solution prepared by dissolving 100 parts of sodium sulfide nonahydrate in 250 parts by volume of 20% caustic soda. The extraction is repeated using 25 parts by volume of the above solution of sodium sulfide. The insolubles are extracted with 75 parts by volume of dioxane. Evaporation of the dioxane gives a product which, after extracting with glacial acetic acid and precipitating with an equal volume of water, is recrystallized from hexane and then alcohol. Its melting point is 100-101 C. It appears to be a new compound since no reference is to be found in the literature. Its analysis is: Calc. for C H Cl: C, 79.5; H, 4.5; Cl, 15.7. Found: C, 79.5; H, 5.3; Cl, 14.3.

Example 6 @l @l 0, ov

Dibenzo [a,h]pyrene-7,14-di0ne solution at 90 C. The insoluble material is isolated by filtering and air-drying. It can be recrystallized from xylene to give pure dibenzo[a,h]pyrene melting at 296- 297.

Example 7 WY L. WY an 003* Pyrauthrone Pyranthrene Example 8 S ll oooH VC--SH The procedure of Example 7 is followed using an equivalent amount of anthraquinone-Z-carboxylic acid in place of the pyranthrone. The product is a mixture of anthracene thiocarboxylic acids and polymers thereof. The reduction of the quinone to the hydrocarbon ring system is shown by infrared spectra. 7

Example 9 O The procedure of Example 7 is followed using an equivalent quantity of G-phenyl-naphthacenequinone in place of pyranthrone, to give l-phenylnaph-thacene.

Example 10 O O H SH I! I OH SH polymers The procedure of Example 7 is followed using an equivalent quantity of alizar-in in place of the pyranthrone. The product is a mixture of polymeric anthracene sulfides and polys-ulfides, in which the reduction of the quinone car-bonyls can be shown by infrared spectra.

Example 11 O HO OHS --r polymers The procedure of Example 7 is followed using an equivalent quantity of anthraquinone-Zeldehyde in place of the pyranthrone. The product is a mixture of polymers of anthracene-Z-thioaldehyde in which the reduction of the quinoid canbonyls can be shown by infrared spectra.

Example 12 8 Example 13 I O O-NI-In The procedure of Example 7 is followed using an equivalent quantity of 3-aminoanthra[2,3-b]benzo- [d] furan- 7,12-dione in place of the pyranthrone. The product is B-aminoanthra [2,3-b] benzo [d] furan.

The procedure of Example 7 is followed using an equivalent quantity of Vat Yellow G C, that is, 1(S), 2(N 5 (S) 6 (N) -bis( z-phenylthiazolo anthraquinone. The product is 1(8), 2(N), 5(5), 6(N)-bis(2-phenylthiazolo)anthracene.

We claim:

l. The process which comprises reducing a member selected from the group consisting of polycyclic aromatic endo-quinones and partial reduction products thereof,. the member being further characterized in that the quinoid ring thereof is fused to at least two other aromatic .rings which comprises heating said member under substantially anhydrous conditions to about to about 250 C. with at least about 3.0 moles of hydrogen sulfide per each quinoid configuration in the presence of at least about 0.1 parts by weight per part of said member of a non-oxidizing acid catalyst.

2. The process of claim 1 in which the catalyst is toluenesulfonic acid.

3. The process of claim 2 in which the endo-quinone is anthraquinone. V

4. The process of claim 2 in which the endo-qu inone is nitroant-hraquinone.

5. The process of claim 2 in which the endo-quinone is dibenzpyrenequinone.

6. The process of claim 2 in which the endo-quinone is pyranthrone.

7. The process of claim 2 in which the endo-quinone is l-chloro-2-methylanthraquinone.

8. The process of claim 1 in which the partially rednced endo-quinone is the hydroqninone form.

9. The process of claim 1 in which the partially reduced 1,878,950 endo-quinone is the anthrone form. 2,620,356 10. The process of claim 1 wherein the catalyst is 5 2,765,301 sulfuric acid. 2,794,046 11. The process of claim 1 wherein the catalyst is 2,794,047 phosphoric acid. r 2,804,452 2,804,453

12. The process of claim 1 wherein the catalyst is -a 10 2 831 893 polyphosphoric acid.

13. The process of claim 1 wherein the catalyst is an alkane sulfonic acid.

References Cited in the file of this patent UNITED STATES PATENTS Ly'ford Sept. 20, 1932 Munday Dec. 2, 1952 Cashion Oct. 2, 1956 Sogn May 28, 1957 Sogn May 28, 1957 Erlesila Aug. 27, 1957 Anderson et a1 Aug. 27, 1957 So'gn Apr. 22, 1958 OTHER REFERENCES Watson: Colour in Relation mo Chemical Constitution, page 3 (1918). 

1. THE PROCESS WHICH COMPRISES REDUCING A MEMBER SELECTED FROM THE GROUP CONSISTING OF POLYCYCLIC AROMATIC ENDO-QUINONES AND PARTIAL REDUCTION PRODUCTS THEREOF, THE MEMBER BEING FURTHER CHARACTERIZED IN THAT THE QUINOID RING THEREOF IS FUSED TO AT LEAST TWO OTHER AROMATIC RINGS WHICH COMPRISES HEATNG SAID MEMBER UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS TO ABOUT 75 TO ABOUT 250*C. WITH AT LEAST ABOUT 3.0 MOLES OF HYDROGEN SULFIDE PER EACH QUINOID CONFIGURATION ION THE PRESENCE OF AT LEAST ABOUT 0.1 PARTS BY WEIGHT PER PART OF SAID MEMBER OF A NON-OXIDIZING ACID CATALYST. 